The present invention relates to a tree shaker assembly including a shaker mechanism and a pair of jaws for engaging a tree or the like and more particularly to means for opening and closing the jaws.
A number of different embodiments of tree shakers are disclosed in the prior art, noting for example U.S. Pat. Nos. 4,223,515 issued Sept. 23, 1980; 4,194,347 issued Mar. 25, 1980; 4,128,986 issued Dec. 12, 1978; 3,793,815 issued Feb. 26, 1974; 3,785,131 issued Jan. 15, 1974; 3,780,510 issued Dec. 25, 1973; 3,762,139 issued Oct. 2, 1973 and 3,163,458 issued Dec. 29, 1964.
Tree shakers of the type disclosed by these various patents have included relatively movable jaws for engaging a tree or the like and different types of shaker mechanisms for oscillating or vibrating the shaker assembly and thereby resulting in vibration of the tree in order to loosen crops such as fruit or nuts from the tree.
In one type of shaker implement, the shaker mechanism was adapted for unidirectional reciprocating movement. Generally, it was found that the unidirectional mode of vibration was generally inefficient because of the need for causing relatively violent shaking of the tree. At the same time, damage could result to the tree.
Accordingly, a second type of shaker mechanism was developed comprising a vibrating device which, after having its jaws engaged with a tree or portion of the tree such as a branch or the like, transmitted power from a motor to the tree by means of repeated vibrations having a high-value fixed frequency (for example, 4,000 cycles per minute). In this manner, very small shock waves may be successively produced for generating a high frequency pulsation, the direction of which changes continuously through a 360.degree. arc, the vibration increasing from the largest branches to the smallest branches of the tree. Such shaker mechanisms are believed to be much more effective in detaching fruit or the like from the tree due to composite effects of resonance and because of other characteristics provided by the shaker mechanism.
The particular shaker mechanism described below in connection with the present invention is a generally conventional design of the second type described above and illustrated, for example, in U.S. Pat. No. 4,128,986 issued Dec. 12, 1978. Accordingly, that reference is incorporated herein as though set out in its entirety in order to disclose a suitable shaker mechanism. However, it is also to be kept in mind that the present invention is not limited to any particular type of shaker mechanism employed in its tree shaking apparatus.
Rather, the present invention is particularly concerned with the method of operating a pair of jaws for engaging clamping pads on the jaws with the tree or the like, for maintaining the clamping pads in engagement with the tree during shaking operation and for subsequently disengaging the clamping pads from the tree.
Operation of the shaker mechanism tends to produce substantial forces which may strip bark off and thereby damage the tree if the jaws are not properly engaged with the tree and apply a strong constant pressure thereon. Accordingly, it is necessary to maintain the jaws in proper engagement with the tree without any slippage. It is also desirable that the tree shaker apparatus be relatively simple yet very effectively designed for assuring operation over long periods of time. There has thus been found to remain a need for a tree shaking attachment which is adapted to overcome problems of the type described above while also providing various operating advantages.